In many agricultural precincts there are large numbers of existing groundwater bores that access aquifers containing brackish water. Brackish water is the term applied to water with concentrations of dissolved salts generally in excess of 2000 mg/L. The salt concentration can be expressed in terms of electrical conductivity (EC). EC is the parameter that is measured in irrigation operation to determined if it is safe to apply water to plants and soil. As a general rule, groundwater bores with EC in excess of 3000 microsiemens per centimeter are unsafe to use for sustained irrigation.
There are three traditional approaches to using brackish water for irrigation. First, the water may be directly used. This suffers from the obvious problems of sensitivity of the plants to salt, leading to yield reductions and the need to leach the soil profile to control salt accumulation, which leads to drainage issues. Ultimately, damage to the soil, loss of yield and poor drainage make this an unattractive solution.
Secondly, there have been attempts to mix, or alternate, brackish water irrigations with fresh water irrigations. This requires exacting management of the water mixing regime, does not eliminate all the problem of yield loss and is attended by the need for leaching to remove salts from the root zone.
Thirdly, desalination through forcing water through a semipermeable membrane by pressurizing brackish water behind the membrane, has been explored as a means of preparing water of suitable quality for sustained irrigation. The desalinated water is stored in a holding tank and then delivered using standard irrigation infrastructure. Typically, this results in expensive water for a number of engineering reasons:                The reverse osmosis systems requires additional infrastructure including a dedicated feed pump, cleaning system and source of electrical power from either a generator or connection to a distributed power supply        The reverse osmosis feed pump operates at high pressure.        Operating conditions in the membrane module predispose the system to precipitation of salts, scaling and fouling.        Capital and Operating costs are high.        